The studies undertaken under the auspices of this grant involve studies on the production of immunoglobulins by man-mouse somatic cell hybrids and the study of certain cell surface antigens by man-mouse hybrid cells. Antigens currently under study include the HC surface protein and CAF or Lets Protein. Techniques being used in the study of immunoglobulin production include radio-immunoelectrophoresis, radio-immunoassay, Ion-exchange chromatography, and affinity chromatography. Results of these studies have led to the assignment of a gene responsible for production of heavy chain immunoglobulins to chromosome 6 in humans. Studies are in progress to assign genes responsible for the production of human immunoglobulin light chains to specific human chromosomes. For examination of cell surface proteins (antigens) two techniques are being employed, surface immunofluorescence and immunoprecipitation of 125I labeled cell surface material. Human chromosomes present in somatic cell hybrids are beind identified using karyotypic analyses of banded chromosome preparations and throught the examination of enzyme markers with known assignments to specific human chromosomes.